Seaside redirect for render not working on physical iOS devices

We're having a problem with physical iOS devices (works fine on Chrome virtual device) where a final Seaside redirect is not happening after an Azure SSO redirect. I'd like to understand what triggers the Seaside redirect: I can see it in normal rendering, but I've never had to dig into it like this before.

When I log from a non-iOS device I see...

1 - WAApplication>>handleFiltered: application URL

• self requestContext redirectTo: 'https://login.microsoftonline.com/...'
• redirects back to our app URL with an access token

2 -WAApplication>>handleFiltered: application URL with MS access token & no _s & _k values

• validate token with Azure
• save user info in new WASession
• finish render

3 - WAApplication>>handleFiltered: application URL with _s & _k plus callback values like: &2=2160&1=3840&3=false

• WAResponse>>location: application URL with _s & new _k and no callback values

4 - WAApplication>>handleFiltered: application URL with _s & _K

• finish render

With iOS step 3 does not happen; I'd like to know what triggers it normally.

Just to add to the fun, we have a two WAApplication registered. The default application fails on iOS, the other works fine. I can see no obvious difference between the two.

Thanks for any help (I'll cross post on the the Seaside mailing list and Discord)

Problem is caused by a seven year old method that used a window.location.href= to gather device characteristics, like screen size and touch support. Removing that href fixes the problem with iOS. Lots of other & cleaner ways to get the data. Quick fix is to wrap the href with a setTimeout for 200 ms.